Amorphous phase distribution in PEE copolymers

The main characteristic feature of highly oriented semicrystalline homopolymers is the existence of a regular sequence of crystalline and amorphous layers placed normally to the orientation axis and giving rise to the long spacing in SAXS. They are linked by a large number of tie molecules. Another peculiarity of oriented polymers is the existence of microfibrils aligned parallel to the orientation axis, as concluded mainly from microscopic observations. Farther, it is known that the amorphous phase is situated mainly inside the fibrils between the crystalline lamellae (intrafibrillar amorphous phase) y whereas a relatively small amount exists between the fibrils interfibrillar amorphous phase). The latter equals 10-15% for poly (ethylene terephthalate) [9] and PBT [10]. 

The structure of oriented multi-block crystallizable copolymers should be basically the same. However, some peculiarities are caused by the limited length of the crystalhzable blocks affecting the interfibrillar and intrafilillar amorphous phase distribution, as weU as the number of tie molecules, discussed below. 

In the present case of multi-block (AB) poly(ether ester)s, the PBT segments are in the crystalline state at room temperature and their length, as 

Equation (1) implicitly assumes that all the amorphous material is situated inside the fibrils between the crystalline lamellae, i.e., it is of interfibrillar type only. The value of 4 thus obtained turned out to be twofold smaller than the lamella thickness, obtained by the Scherrer equation [3]. For this reason, 

It can be concluded that, in contrast to homopolymers, the interfibrillar amorphous material fraction in the case of poly (ether ester)s is large (30-80%). 

---